This book constitutes the proceedings of the 21st International Conference on Parallel and Distributed Computing, Applications, and Technologies, PDCAT 2020, which took place in Shenzhen, China, during December 28-30, 2020.The 34 full papers included in this volume were carefully reviewed and selected from 109 submissions.

Blood leukocyte object detection according to model-parameter transfer and deformable convolution.- Heterogeneous Software Effort Estimation via Cascaded Adversarial Auto-Encoder.- A Novel Distributed Reinforcement Learning Method for Classical Chinese Poetry Generation.- Memory Access Optimization of High-order CFD Stencil Computations on GPU.- The Dataflow Runtime Environment of DFC.- Adaptive Tensor-Train Decomposition for Neural Network Compression.- Development of a UAV path planning approach for multi-building inspection with minimal cost.- Construction of Completely Independent Spanning Tree based on Vertex Degree.- Distributed Algorithm for Truss Maintenance in Dynamic Graphs.- Short-term load forecasting based on CNN-BiLSTM with Bayesian Optimization and Attention Mechanism.- On The Non-ergodic Convergence Rate of The Directed Nonsmooth Composite Optimization.- 6D Pose Estimation Based on the Adaptive Weight of RGB-D Feature.- Blockchain-based Secure Outsourcing of Fully Homomorphic Encryption using Hidden Ideal Lattice.- Multiple Projections Learning for Dimensional Reduction.- Preventing DDoS Attacks on Bitcoin Memory Pool by the Dynamic Fee Threshold Mechanism.- The Compiler of DFC: A Source Code Converter that Transform the Dataflow Code to the Multi-threaded C Code.- Online Learning-Based Co-Task Dispatching with Function Configuration in Edge Computing.- System-Level FPGA Routing for Logic Verification with Time-Division Multiplexing.- Protein interresidue contact prediction based on deep learning and massive features from multi-sequence alignment.- See Fine Color from the Rough Black-and-White.- Data Aggregation Aware Routing for Distributed Training.- A New Integer Programming Model for the File Transfer Scheduling Problem.- Approximation Algorithms for the General Clustered Routing Problem.- Maximizing Group Coverage in Social Networks.- LightLayers: Parameter Efficient Dense and Convolutional Layers for Image Classification.- The Hybrid NavigationMethod in Face of Dynamic Obstacles.- A relaxed balanced lock-free binary search tree.- A Dynamic Parameter Tuning Method for High Performance SpMM. -Data Caching Based Transfer Optimization in Large Scale Networks.- Second-order Convolutional Neural Network based on Cholesky Compression Strategy.- Submodular Maximization with Bounded Marginal Values.- A streaming model for monotone lattice submodular maximization with a cardinality constraint.- The prize-collecting $k$-Steiner tree problem.- Optimal algorithm of Isolated toughness for Interval Graphs.- Graceful Performance Degradation in Apache Storm.